This invention relates to a slide resistor and more specifically to a slide resistor of the type wherein the resistance element consists of an insulating support mounted on an electrically conductive collector element and provided with a resistance layer, the slider carrying the sliding contact spring being guided by the collector element.
Adjustable slide resistors of this type are often used with appliances in the audio and video field for controlling operational values, such as sound, contrast, volume, brightness, and the like. In contrast to rotary variable resistors, slide resistors have the advantage that they allow a better control of the intended adjustment along a linear scale. Slide resistors have been used for some time in studio equipment; they are now becoming usual also in domestic installations, e.g. in connection with dimmers and timers, where they replace rotary resistors.
An electrical device for controlling the brightness of a lamp is known, which device is adapted to be mounted in a commercially available flush-mount box and includes a carrier plate which is provided at its lower side with conductor strips and a coil and at its upper side with a rotary resistor combined with a push button switch having a shaft for an actuating knob, terminals for connecting lines and other electronic elements.
Slide resistors are increasingly employed in dimmers of this kind to take advantage of their improved position-indicating facility.
In a prior art resistor consisting essentially of a resistance element mounted on an insulating plate, a collector element and a slider having a slider contact spring and terminals for the electrical connections, the collector element is formed as a flat stamped metal part having a bent edge. The collector element carries both the slider and the insulating plate with the resistance element mounted thereon. A corresponding profile of the collector element provides a guide for the slider which engages the upper portion of the collector element having the bent edge in a manner free of play. As generally required with profile guides, the slider must be manufactured with close tolerances to achieve a smooth sliding motion. This, however, increases the costs of such a slide resistor which is produced in large quantities. Another slide resistor is known in which the slider is guided by a bent edge of the collector element, the edge engaging in a groove formed on the inner side of the slider. The resistance element and the collector element are mounted in parallel relation on an insulating plate. The slider is formed with short projections extending around an edge of the insulating plate to prevent the slider from tilting. By disposing the resistance element and the collector element parallel to each other on the insulating plate, a slide resistor of a small structural height is obtained, provided that the plane of the insulating plate extends parallel to the printed circuit board to which the slide resistor is soldered. However, when the plane of the insulating plate extends perpendicularly to the printed circuit board, the space required in the lateral direction is small but the height is considerable. This is particularly disadvantageous in electrical wiring devices because the limited available space is mainly taken by electronic elements. This is especially true for those devices which function as timers or the like in addition to the dimmer function and therefore require additional electronic elements.
It is an object of the invention to provide a slide resistor in which the above disadvantages are overcome. It is a further object of the invention to devise a slide resistor which requires little space with respect to both height and width. As another object of the invention, a slide resistor is to be provided which allows a smooth sliding movement. It is a still further object of the present invention to provide a slide resistor which is of uncomplicated design and lends itself to mass production.